Compilare: main.cpp: In function 'bool isOK(int)': main.cpp:28:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < digits.size() / 2; ++i) { ~~^~~~~~~~~~~~~~~~~~~ main.cpp:11:6: warning: unused variable 'tx' [-Wunused-variable] int tx = x; ^~ main.cpp: In function 'int main()': main.cpp:53:32: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("fibo.in", "r", stdin); ^ main.cpp:54:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("fibo.out", "w", stdout); ^ main.cpp:74:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^